无法访问表单中的关联模型属性

Question

我正在尝试为 has_many :through 关系构建一个表单。问题是，我可以从表单中的连接表（：通过）访问属性，但不能访问其他表。

我的模型如下所示：

class Recipe < ActiveRecord::Base
   has_many :quantities
   has_many :ingredients, through: :quantities
   accepts_nested_attributes_for :quantities
end

class Quantity < ActiveRecord::Base
  belongs_to :recipe
  belongs_to :ingredient
end

class Ingredient < ActiveRecord::Base
  has_many :quantities
  has_many :recipes, through: :quantities 
end

我的表格：

<%= form_for(@recipe) do |f| %>
  <div class="field">
    <%= f.label :title %><br>
    <%= f.text_field :title %>
  </div>
  <div class="field">
    <%= f.label :description %><br>
    <%= f.text_area :description %>
  </div>


  <div class="quantities">
    <%= f.fields_for :quantities do |builder| %>
      <%= render 'quantity_fields', :f => builder%>
    <% end %>
    <%= link_to_add_association 'Add', f, :quantities %>
  </div>
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

以及数量字段部分：

<p>
<%= f.label :value, "Value" %>
<%= f.text_field :value %>
<%= f.label :unit, "Unit" %>
<%= f.text_field :unit %>
<%= f.text_field :ingredient %>
<%= f.fields_for :ingredient do |builder|%>
  <%= builder.label :name, "Ingredient"%>
  <%= builder.text_field :name %>
<% end %>
</p>

数量属性的字段是正确的，但成分名称的文本字段（在数量字段部分内）保持为空。 另一方面，在 Rails 控制台上，我可以轻松地在数量对象上使用成分方法并获得结果。

我一直在尝试找到解决这个问题的方法，这让我非常沮丧。我确信这是一项标准任务，我只是遗漏了一小部分。谁能帮帮我？

编辑：

另外，当我将配方表更改为直接渲染成分时，它不起作用。文本字段保持为空。

<%= form_for(@recipe) do |f| %>
  <div class="field">
    <%= f.label :title %><br>
    <%= f.text_field :title %>
  </div>
  <div class="field">
    <%= f.label :description %><br>
    <%= f.text_area :description %>
  </div>

  <div class="ingredients">
    <%= f.fields_for :ingredients do |builder| %>
      <p>
      <%= builder.label :name, "Name" %>
      <%= builder.text_field :name %>
      <%= builder.label :description, "Description" %>
      <%= builder.text_field :description %>
      </p>
    <% end %>
  </div>

  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

编辑 2： 配方控制器：

class RecipesController < ApplicationController
  before_action :set_recipe, only: [:show, :edit, :update, :destroy]

  # GET /recipes
  # GET /recipes.json
  def index
    @recipes = Recipe.all
  end

  # GET /recipes/1
  # GET /recipes/1.json
  def show
  end

  # GET /recipes/new
  def new
    @recipe = Recipe.new
  end

  # GET /recipes/1/edit
  def edit
  end

  # POST /recipes
  # POST /recipes.json
  def create
    @recipe = Recipe.new(recipe_params)

    respond_to do |format|
      if @recipe.save
        format.html { redirect_to @recipe, notice: 'Recipe was successfully created.' }
        format.json { render :show, status: :created, location: @recipe }
      else
        format.html { render :new }
        format.json { render json: @recipe.errors, status: :unprocessable_entity }
      end
    end
  end

  # PATCH/PUT /recipes/1
  # PATCH/PUT /recipes/1.json
  def update
    respond_to do |format|
      if @recipe.update(recipe_params)
        format.html { redirect_to @recipe, notice: 'Recipe was successfully updated.' }
        format.json { render :show, status: :ok, location: @recipe }
      else
        format.html { render :edit }
        format.json { render json: @recipe.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /recipes/1
  # DELETE /recipes/1.json
  def destroy
    @recipe.destroy
    respond_to do |format|
      format.html { redirect_to recipes_url, notice: 'Recipe was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_recipe
      @recipe = Recipe.find(params[:id])
    end

    # Never trust parameters from the scary internet, only allow the white list through.
    def recipe_params
      params.require(:recipe).permit(:title, :description, quantities_attributes: [:value, :unit, :recipe, :ingredient, :_destroy])
    end
end

Answer 1

当以这种方式使用has_many :through 关联时，您可以像这样设置模型：

class Recipe < ActiveRecord::Base
   has_many :quantities
   has_many :ingredients, inverse_of: :recipes

   accepts_nested_attributes_for :quantities
end

class Quantity < ActiveRecord::Base
  belongs_to :recipe
  belongs_to :ingredient

  accepts_nested_attributes_for :ingredients
end

class Ingredient < ActiveRecord::Base
  has_many :quantities
  has_many :recipes, inverse_of: :ingredients 
end

This article 在类似的上下文中使用 has_many :through 关联覆盖嵌套属性。希望这会有所帮助！